Rotary piston machine

ABSTRACT

A rotary piston machine including a rotary piston ( 6 ), which is mounted oil the crank pin ( 5, 5 ′) of a crankshaft accommodated in a stationary housing ( 1 ) and held by a holding device ( 8, 9, 10, 11 ) in a manner that prevents significant change of the angular position of the rotary piston relative to the housing. The rotary piston forms, on its periphery, at least one pair of concave and convex surfaces ( 12, 13; 12′, 13 ′) that engage with an associated pair of convex and concave surfaces ( 14, 15; 14′, 15 ′) located on a peripheral surface ( 3 ) of the housing surrounding the rotary piston. The pairs of concave and convex surfaces engage one another over the angular range of the rotation of the crankshaft while forming a chamber and while altering the size of the chamber over this angular range. The holding device has a bearing device ( 9, 10, 11 ), which is situated at a distance from the crankshaft (M 1 ) and with which the rotary piston ( 6 ) is mounted on the housing ( 1 ) in a manner that enables it to rotate around an arbor ( 9 ) that is parallel to the crankshaft (M 1 ) and to be displaced toward the crankshaft. The distance between the crankshaft (M 1 ) and the pivot bearing ( 9 ) of the hearing device ( 9, 10, 11 ) is adjustable.

[0001] The present invention relates to a rotary piston machine.

[0002] A rotary piston machine with the features of group a of claim 1is known from EP 0644981 B1. To understand the generic machine type,reference is made to the complete contents of said publication.

[0003] As disclosed by said publication, this machine type comprises apiston that is mounted on the crank pin of a crankshaft accommodated ina housing and, at the same time, makes a parallel rotation, whilemaintaining its angular position with regard to the housing. This typeof rotation is called parallel rotation below.

[0004] As is also described in detail in said publication, the pistoncomprises, on its periphery, one or more pairs of convex and concavesurfaces, which engage with and disengage from associated concave andconvex surfaces of a peripheral wall of the housing, while forming achamber. During this chamber-forming engagement, the convex surface ofthe piston extends on the concave surface of the peripheral wall and theconcave surface of the piston extends on the convex surface of theperipheral wall, both in a sealing manner, thus enclosing a chamber thatis also sealed laterally, by sidewalls of the housing in the case of thepublication named. While the rotation during the chamber-formingengagement is in progress, the volume of the chamber changes, and thisat a compression ratio that is, to advantage, very high.

[0005] As is described in said publication, a machine of such type canbe used for a plurality of purposes, for example as a pump, as acombustion engine and, in particular, as a gas compressor that is ableto achieve a very high compression in one stage, that is in one chamber.

[0006] If the piston is mounted on a crankshaft, the angular position ofthe piston in relation to the crankshaft is, initially, not defined.Hence, a holding device is required that prevents the angular positionof the piston with regard to the housing from changing on rotation ofthe crankshaft. To achieve this, the known construction mentionedprovides one or more additional eccentric shafts on which the piston ismounted and which are rotating in an angle-synchronized manner.

[0007] The necessary several crankshafts that are mounted in the pistonare disadvantageous in the known construction. Said crankshafts must bespaced apart, thus involving high space requirements inside the pistonand limiting the constructive possibilities to a considerable degree.Moreover, the crank pin bearings in the piston, since being spacedapart, must be arranged at the edge of the piston, that is near thechambers formed on the latter's periphery where they are subject to ahigh thermal load. This causes problems in connection with thedurability of the machine.

[0008] A rotary piston machine with the features of group b of claim 1is known from DE 32 31 756 A1. This publication discloses a machinecomprising a helical piston that is driven to make parallel rotations,as in the aforementioned known construction. As is shown in FIGS. 3 and4 of this publication, a bearing device that is spaced apart from thecrankshaft is provided as holding device for parallel arrangement of thepiston. The construction of this bearing device is essentially simplerthan that provided in the publication first mentioned, which comprisesadditional crankshafts. In addition, it results in a rotary motion thatis parallel only approximately and has a minor tendency to tilt thatcan, however, be tolerated if the distance between the crankshaft andthe bearing device is selected to be accordingly wide or can becompensated by minor changes in the shape of the chamber-formingsurfaces on the piston and/or the peripheral wall, so that there willnot be any leakage problems. The resultant constructive possibilities ofarranging the chamber-forming wall regions are considerably morenumerous. Moreover, the machine can be designed smaller while ensuringthe same output, and it also has thermal benefits. The bearing devicecan be formed according to the alternatives shown in FIGS. 3 and 4 of DE32 31 756 A1, wherein the piston is either rotatively mounted on aparallel slide block, or displaceable in longitudinal direction in apivoted slide block.

[0009] All of the known constructions mentioned have the disadvantagethat the kinematics of the piston movement is defined and can not bechanged.

[0010] The invention aims at providing a rotary piston machine havingthe advantages of the two known constructions mentioned, however withpiston motion kinematics that can be changed.

[0011] On the basis of the features of group c of claim 1, the runningkinematics of the piston can be readjusted by changing the distancebetween the crankshaft and the pivot bearing of the bearing device suchthat, with the distance being greater, the running motion ratherapproximates the strict parallel rotation where no tilting occurs and,with the distance being shorter, the tilting motion increases. Strongertilting motion and/or any deviation from a standard length,respectively, to which the chamber surfaces are adjusted will result inleaks in the chambers. Of this fact advantage can be taken, for example,by having the machine run at idle speed with a high degree of leakage,that is with low power consumption and rotund running.

[0012] The features of claim 2 are provided advantageously. With thisconstruction, the piston can be designed in the known manner andaccording to the aforementioned publication. The holding rod is attachedat an appropriate point and extends to the bearing device that isarranged at a distance.

[0013] Preferably, the crank pins are arranged in the piston at a pointthat is subject to a low thermal load, that is to say at a point that isspaced apart from the chamber-forming walls. For that reason, thefeatures of claim 3 that are, as such, known from DE 195 00 774 A1 arepreferably provided. As a result, the crank pin bearing is entirelytaken out of the piston and is arranged next to it. Thereby, the thermalproblems arising at the crank pin bearing can be solved in an extremelyefficient manner if the crank pin bearing is, for example, arranged at apoint that is passed by fresh air.

[0014] Preferably, the features of claim 4 are provided. Apiston/cylinder arrangement enables the displacement capability requiredfor the bearing device. With such a construction, the pivot bearing canbe provided in a simple manner, either by mounting the holding rod inthe piston on a pivot bearing in the manner of a connecting-rod bearingor by mounting the cylinder to the housing on a pivot bearing. Thisresults to the advantage, that the piston/cylinder arrangement can beused as a further compression or expansion chamber, for example as arecompression stage of a compressor.

[0015] The only figure of the drawing shows a sectional view intransverse direction to the crankshaft of a rotary piston machineaccording to the invention.

[0016] The rotary piston machine shown comprises a stationary housing 1that encloses an interior region 2 with in internal peripheral wall 3.In parallel to the plane of the drawing, the interior region 2 is closedby a plane lateral wall 4 that is positioned below the plane of thedrawing. A lateral wall that is not shown and is positioned above theplane of the drawing is arranged in parallel to the lateral wall 4.

[0017] A crankshaft with center point M1 that comprises a radiallyoffset crank pin 5 with center point M2 is mounted in the lateral wall 4and the other lateral wall that is arranged in parallel thereto. Onrotation of the crankshaft, the crank pin 5 rotates with its centerpoint M2 on the broken circular line about the center point M1 of thecrankshaft.

[0018] A rotary piston 6 is mounted on the crank pin 5. A holding pin 8is mounted in a hole 7 within said rotary piston 6. The free end of theholding rod 8 is mounted via a pivot bearing 9, with an axis in parallelto the crankshaft, in a reciprocating piston 10 that is running in acylinder 11 attached to the housing 1, with its cylinder axis orientedtowards the region of the crankshaft.

[0019] While the crank pin 5 is rotating about M1, it is obvious that,as a result, the reciprocating piston 10 is moving in the cylinder 11 ina reciprocating manner, with the holding rod 8 slightly rotating aboutthe pivot bearing 9 in the reciprocating piston 10. Thus, thepiston/cylinder arrangement 10, 11 forms a bearing device for the rotarypiston 6 which, in essence, holds the latter in its angular positionwith regard to the housing 1, with only a slight tilting motion when itcarries out its parallel rotation. This tilting motion depends on thedistance between the crankshaft and the bearing device 9, 10, 11. Withthe distance being great, the tilting motion is so small that it can beneglected, resulting in an approximately genuine parallel rotation.

[0020] A first pair of surfaces comprising a convex surface 12 and aneighboring concave surface 13 is provided on the periphery of therotary piston 6. An associated first pair of surfaces comprising aconcave surface 14 and a convex surface 15 is arranged on the peripheralsurface 3 of the housing 1. In the shown angular position of the crankpin 5, wherein the crank pin rotates about the crankshaft in clockwisedirection, a chamber has just been closed between the surface pairs 12,13 and 14, 15, by sealing the convex surface 12 on the concave surface14 (at point A) and by sealing the concave surface 13 on the convexsurface 15 (at point B) as well as by the lateral walls 4. Whilerotation of the crank pin 5 continues, the convex surface 12 of therotary piston is running across the concave surface 14 of the peripheralwall in a sealing manner. Likewise, the concave surface 13 of the rotarypiston is running across the convex surface 15 of the peripheral wall.The chamber formed between the walls is constantly reducing its volumebecause the sealing points A and B are approaching one another. After aspecific rotational angle of the crank pin 5, the rotary piston 6 liftsfrom the peripheral wall 3 and opens the chamber and then, in theposition shown in the figure, closes the chamber again, with the chambernow having a large volume.

[0021] With the illustrated sense of rotation of the crank pin 5 aboutthe crankshaft in clockwise direction, this results in a chamber thatrepeatedly closes when having a large volume, then reduces its volumeand then opens. This construction can be used as a compressor. In thiscase, gas flows through an inlet opening 16 into the interior region 2of the housing 1 at low pressure, is enclosed while the chamber isclosing and compressed while the rotary piston 6 continues its rotation.The chamber reaches its smallest volume at a point where an outlet valve17 is provided, which can be provided as a simple check valve that opensto the outside and which is connected to a high-pressure duct 18,through which the compressed gas via appropriate connection devices isdischarged.

[0022] In the example shown, a further pair of surfaces forming a secondchamber in like manner is provided each on the rotary piston 6 and onthe housing 1. The description above is also applicable to this chamber.The parts of this chamber are provided with the reference marks of thechamber described above, with these reference marks being identified bya prime. In the example, the second chamber operates phase-delayed. Ifone chamber closes and compresses, the other chamber is open, thus beingable to suck in fresh gas through the inlet opening 16′.

[0023] As regards possible constructive variants of the rotary piston 6and the chamber-forming details as well as the possibilities of usingthis construction as a compressor, combustion engine or the like,reference is made to the contents of EP 0644981 B1. Any variantillustrated there can also be executed here.

[0024] In the shown example of the present invention, the bearing device9, 10, 11 is designed with a reciprocating piston 10 and a cylinder 11,in order to ensure that the rotary piston 6 is mounted on a pivotbearing. This piston/cylinder arrangement can be used as compression orexpansion chamber; to achieve this, the cylinder chamber below thereciprocating piston 10 must be formed to comprise inlet and outletducts with the appropriate valves, none of which are shown here. If theconstruction shown is used as a compressor, the two chambers that areformed on the rotary piston 6 by the surface pairs can, for example, bedesigned with different sizes and can operate as precompression orrecompression stage, while the piston/cylinder arrangement 10, 11 isused as a third recompression stage.

[0025] The bearing device at the free end of the holding rod 8, however,can be formed in an entirely different manner, wherein it must only beensured that both a tilting motion and a reciprocating motion indirection towards the crankshaft M1 is permitted. For example, in asimple alternative of the shown piston/cylinder arrangement 10, 11, theholding rod 8 is attached to the reciprocating piston 10 in a rigidmanner and the cylinder 11 is mounted on the housing 1 in a pivotingmanner. The bearing device can also be formed to comprise the samekinematics, but without a piston/cylinder unit being formed.

[0026] Since, in the construction according to the invention, the rotarypiston 6 is only mounted on a crank pin 5, in contrast to the knownconstructions, said crank pin can be arranged at any point in thepiston. It is, in particular, possible that it is arranged at a very fardistance from the chamber-forming surfaces 12, 13 or 12′, 13′respectively. This reduces the heat transfer from the very hot chambersto the bearings of the crank pin 5 and the crankshaft, so that these aresubject to a lower thermal load. In a constructive variant, thecrankshaft can be arranged outside of the rotary piston 6 at a pointthat is thermally well protected. This variant is shown by broken linesin the figure. The crankshaft is mounted at M1′ in a lateral bulging 3′of the peripheral wall 3. The crank pin 5′ is mounted in a bearing eye19 that is attached to the rotary piston 6 by means of an arm 20 or asimilar projection of the rotary piston 6. At this point, i.e. in theregion of fresh air and far away from the chamber-forming surfaces, thecrankshaft is arranged at a point thermally well protected.

[0027] The crank pin can also be arranged at a different point that isnot illustrated here and is situated far away from the thermally loadedregion of the rotary piston 6. Preferrably, the distance between thecrank pin bearing 19 and the bearing device 9, 10, 11 should be selectedas great as possible, in order to minimize the tilting motion of therotary piston 6. For that reason, the crankshaft bearing should,preferrably, be provided on that side of the rotary piston that pointsaway from the bearing device.

[0028] As already mentioned, the shown rotary piston machine accordingto the invention results in an approximate parallel rotation of therotary piston 6 which is, however, superimposed by a slight cyclictilting motion. The chamber-forming surfaces 12, 13; 14, 15 of the onechamber that are formed almost in the shape of a circular arc in theplane of the drawing and the corresponding surfaces of the other chamberthat are identified by a prime must, in comparison with the exactcircular shape known from EP 06449081 B1, be varied to a minor degree,in order to ensure that the chamber is always closed in a sealing mannerin case of the parallel rotation with superimposed tilting motionaccording to the invention. The curve shapes to be calculated result ata specific distance of the center point M1 of the crankshaft from thebearing device 9, 10, 11. Then the machine illustrated operates with thechamber being sealed in an optimum manner.

[0029] It is, however, possible to vary the distance between thecrankshaft and the bearing device 9, 10, 11. To achieve this, theholding rod 8 in the hole 7 of the rotary piston 6 can, for example, beformed to be adjustable so that it can, for example, be readjusted fromthe end position 8′ to 8″. A readjustment from position 8′ to position8″ results in a reduced distance between the bearing device and thecrankshaft and, thus, in an increased tilting motion. If thechamber-forming surfaces at the rotary piston 6 and at the peripheralwall 3 are calculated for position 8′, they cannot seal completely atposition 8″ any longer.

[0030] However, this can be used to advantage for specific purposes. Ifthe chambers are sealing only incompletely, the power consumption of thecompressor decreases, this resulting in more rotundic running. Hence,such a setting is, for example, suitable to be used as setting in theidle mode.

1. A rotary piston machine, comprising: a) a rotary piston (6), saidrotary piston being rotatably mounted on a crank pin (5, 5′) of acrankshaft accommodated in a stationary housing (1) and being held by aholding device (8, 9, 10, 11) for preventing an angular position of therotary piston, relative to the housing, from significantly changing,said rotary piston forms, on its periphery, at least one pair of concaveand convex surfaces (12, 13; 12′, 13′), said at least one pair ofconcave and convex surfaces engaging an associated pair of convex andconcave surfaces (14, 15; 14′, 15′) located on a peripheral surface (3)of the housing, said housing peripheral surface surrounding the rotarypiston, the pairs of concave and convex surfaces engage one another overan angular range of crankshaft rotation while forming a chamber andwhile altering the size of the chamber over this angular range, b)wherein the holding device has a bearing device (9, 10, 11), saidbearing device being situated a distance from the crankshaft (M1) andserving to mount the rotary piston (6) on the housing (1) in a mannerthat enables the rotary piston to rotate around an axis (9) that isparallel to the crankshaft (M1) and to be displaced toward thecrankshaft, c) wherein a distance between the crankshaft (M1) and apivot bearing (9) of the bearing device (9, 10, 11) is adjustable. 2.The rotary piston machine according to claim 1, wherein the rotarypiston (6) is connected to the bearing device (9, 10, 11) via a holdingrod (8).
 3. The rotary piston machine according to claim 1, wherein therotary piston (6) carries the crank pin bearing (19) that is spacedapart via an arm (20).
 4. The rotary piston machine according to claim1, wherein the bearing device (9, 10, 11), as a device for displaceablebearing, comprises a piston/cylinder arrangement (10, 11).